The present invention relates to a straight edge clamping device. More particularly, the invention relates to a straight edge clamping device used to secure workpieces and to guide a power tool along the straight edge.
Straight edge clamps are used in wood working for having a straight edge secured to a workpiece or workpieces so that a power tool or a guide for a power tool can be moved along the straight edge, for example, to form a cut edge with a circular hand saw or to form a trimmed edge with a hand router. Also, straight edge clamps are used for the purpose of holding accessory tool against a workpiece, for example, to form pocket holes.
A straight edge clamp by prior art includes a straight edge that is made of extruded aluminum and has an open channel, a fixed stop, a sliding stop that is received in the channel and can slide along the straight edge, and a bar or rod clamp. The sliding stop has a body that is inserted in the channel of the straight edge, and a jaw that protrudes from the body and out of the channel to secure a workpiece.
The shape of the straight edge, thickness of its cross-section, and manufacturing tolerance of extruded aluminum affects the stability of the straight edge when working on workpieces, such as making a cut with a hand circular saw, or hand router, or drilling pocket holes with an attached accessory tool.
When the workpiece are clamped between the fixed stop and the sliding stop with the clamping action of the bar clamp, the jaw of the sliding stop is forced against the workpiece, and the body of the sliding stop binds itself within the channel of the straight edge between the top and bottom surfaces of the channel.
The problem in a straight edge clamp by prior art is that aluminum extrusion products used for making straight edges has a minimum dimension variation of 20 mil, and this variation is the potential amount of movement of the straight edge even when the bar clamp of the straight edge clamp is securely engaged. The problem is inherent in the nature of aluminum extrusion.
The variation is affected by many factors such as shape, size and thickness of the straight edge. Such factors also affect the cost of the extrusion and ultimately the cost of the straight edge. Increasing the thickness of the straight edge for example will decrease the manufacturing dimension variation and increase accuracy and usability of the straight edge clamp. However, it increases the ultimate manufacturing cost of the straight edge clamp beyond practicality.
Accordingly, there has been a demand for a more stable straight edge clamp without any appreciable difference in manufacturing cost.
The present invention is contrived to overcome the conventional disadvantages. Therefore, an object of the invention is to provide a straight edge clamp having improved stability of its position while the clamp is engaged without increasing the manufacturing cost of the clamp.
Another object of the invention is to provide a straight edge clamp that enables a power tool to cut a workpiece more accurately when the workpiece is secured by the clamp.
To achieve the above-described objects, in accordance with an embodiment thereof, the invention provides a straight edge clamping device for clamping workpieces that comprises an elongated hollow base having a constant cross-section and having a first end, a second end, a flat lower wall for contacting workpieces, an upper wall, and two sidewalls connecting the lower wall and the upper wall, a first stop fixed at the first end of the base, a second stop movably provided along the base, and a clamp for holding the workpieces together. The lower wall of the base has an opening, and the opening, the lower wall, the upper wall, and the sidewalls of the base define a channel. The second stop has a body movably received in the channel of the base and a stop for securing the workpieces. The body of the second stop has a shape reverse to the shape of the channel of the base so that the body and the channel interlock. The upper wall of the base has one or more recesses, and the body of the second stop has one or more projections having a shape reverse to the shape of the recesses so that the recesses and the projections interlock.
The base may further comprise two slant walls between the sidewalls and the upper wall. The angle between the slant walls and the sidewalls is approximately 45 degrees.
The first stop has a body inserted in the channel of the base and a stop for securing the workpieces. The body of the first stop has a shape reverse to the shape of the channel of the base so that the body and the channel interlock. The body of the first stop has one or more projections having a shape reverse to the shape of the recesses so that the recesses and the projections interlock.
The recess of the base is rectangular and has a depth of approximately one sixteenth of an inch, and wherein the projection of the second stop is rectangular and has a height of approximately one sixteenth of an inch.
The recess of the base is rectangular and has a depth of approximately one eighth of an inch, and wherein the projection of the second stop is rectangular and has a height of approximately one eighth of an inch.
The upper wall of the base may further comprise a guide channel, and the clamping device may further comprise a drill guide movably provided along the base. The drill guide has a fastener that is guided in the guide channel of the base.
In accordance with another embodiment thereof, the invention provides a straight edge clamping device for clamping workpieces that comprises an elongated hollow base having a constant cross-section and having a first end, a second end, a flat lower wall for contacting workpieces, an upper wall, and two sidewalls connecting the lower wall and the upper wall, a drill guide attached at the first end of the base, a first stop movably provided along the drill guide, a second stop movably provided along the base, and a clamp for holding the workpieces together. The lower wall of the base has an opening, and the opening, the lower wall, the upper wall, and the sidewalls of the base define a channel. The second stop has a body movably received in the channel of the base and a stop for securing the workpieces. The body of the second stop has a shape reverse to the shape of the channel of the base so that the body and the channel interlock. The upper wall of the base has one or more recesses, and the body of the second stop has one or more projections having a shape reverse to the shape of the recesses so that the recesses and the projections interlock.
The advantages of the present invention are: (1) the straight edge clamp is kept stable after the workpieces are clamped and during wood working on the workpieces; (2) Woodworking accuracy of the finished product improves; and (3) the improved straight edge clamp can be manufactured without increasing the manufacturing cost appreciably.